U.S. patent application number 12/279529 was filed with the patent office on 2009-03-12 for polylactic acid resin composition and molded item.
Invention is credited to Norio Fukawa, Masatoshi Iji, Kazuhiko Inoue, Yohei Kabashima, Hiroo Kamikawa, Shin Serizawa, Kazue Ueda, Tsunenori Yanagisawa.
Application Number | 20090069463 12/279529 |
Document ID | / |
Family ID | 38371653 |
Filed Date | 2009-03-12 |
United States Patent
Application |
20090069463 |
Kind Code |
A1 |
Serizawa; Shin ; et
al. |
March 12, 2009 |
POLYLACTIC ACID RESIN COMPOSITION AND MOLDED ITEM
Abstract
Provided is a polylactic acid resin composition obtained by
adding a carboxylic acid amide and a carboxylic acid ester each of
which has at least one polar group in a molecule to a polylactic
acid resin reacted with a (meth)acrylate compound. Also provided is
a polylactic acid resin molded article which is a molded article
obtained by molding the polylactic acid resin composition,
manufactured by setting a mold temperature to a glass transition
temperature of a polylactic acid resin plus 20.degree. C. or higher
and a melting point thereof minus 20.degree. C. or lower, at the
time of injection molding the polylactic acid resin composition.
Thus, a resin composition in which a moldability is improved at a
temperature at which a polylactic acid resin is crystallized, and a
molded article therefrom are provided.
Inventors: |
Serizawa; Shin; (Tokyo,
JP) ; Yanagisawa; Tsunenori; (Tokyo, JP) ;
Inoue; Kazuhiko; (Tokyo, JP) ; Iji; Masatoshi;
(Tokyo, JP) ; Kabashima; Yohei; (Kyoto, JP)
; Ueda; Kazue; (Kyoto, JP) ; Kamikawa; Hiroo;
(Kyoto, JP) ; Fukawa; Norio; (Kyoto, JP) |
Correspondence
Address: |
YOUNG & THOMPSON
209 Madison Street, Suite 500
ALEXANDRIA
VA
22314
US
|
Family ID: |
38371653 |
Appl. No.: |
12/279529 |
Filed: |
February 13, 2007 |
PCT Filed: |
February 13, 2007 |
PCT NO: |
PCT/JP2007/052897 |
371 Date: |
August 14, 2008 |
Current U.S.
Class: |
524/9 ;
264/328.1; 524/284 |
Current CPC
Class: |
C08K 5/10 20130101; C08L
51/08 20130101; C08L 67/07 20130101; C08K 5/14 20130101; C08K 5/29
20130101; C08F 222/38 20130101; C08L 71/02 20130101; C08F 289/00
20130101; C08J 5/045 20130101; C08J 2367/04 20130101; C08L 51/08
20130101; C08J 2367/06 20130101; C08K 5/20 20130101; C08J 5/04
20130101; C08J 2367/07 20130101; C08L 67/07 20130101; C08L 2666/02
20130101; C08L 2666/02 20130101 |
Class at
Publication: |
524/9 ; 524/284;
264/328.1 |
International
Class: |
C08K 5/20 20060101
C08K005/20; C08K 11/00 20060101 C08K011/00; B29C 45/00 20060101
B29C045/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 14, 2006 |
JP |
2006-035892 |
Claims
1. A polylactic acid resin composition, comprising: a polylactic
acid resin reacted with a (meth)acrylate compound; and at least one
kind of low molecular compound selected from a carboxylic acid
amide and a carboxylic acid ester each of which has a polar group
in a molecule.
2. A polylactic acid resin composition according to claim 1,
wherein the polar group comprises at least one kind of group
selected from the group consisting of an oxygen-containing
substituent, a nitrogen-containing substituent, and a halogen
group.
3. A polylactic acid resin composition according to claim 1,
wherein the polar group comprises at least one kind of group
selected from the group consisting of a hydroxyl group, a glycidyl
group, a carboxyl group, an amino group, a nitro group, a cyano
group, and an isocyanate group.
4. A polylactic acid resin composition according to claim 1,
wherein the at least one kind of low molecular compound selected
from a carboxylic acid amide and a carboxylic acid ester each of
which has a polar group in a molecule comprises an
ethylenebis-12-hydroxystearic acid amide.
5. A polylactic acid resin composition according to claim 1,
wherein the polylactic acid resin composition contains 100 parts by
mass or less of a fiber with respect to 100 parts by mass of the
polylactic acid resin.
6. A polylactic acid resin composition according to claim 5,
wherein the fiber comprises at least one kind of fiber selected
from a plant-derived fiber, a synthetic organic fiber, and an
inorganic fiber.
7. A polylactic acid resin composition according to claim 5,
wherein the fiber has an average fiber length of 80 .mu.m to 3 mm
after being mixed with the polylactic acid resin.
8. A polylactic acid resin molded article, which is obtained by
molding a polylactic acid resin composition, wherein the polylactic
acid resin composition comprises: a polylactic acid resin reacted
with a (meth)acrylate compound; and at least one kind of low
molecular compound selected from a carboxylic acid amide and a
carboxylic acid ester each of which has a polar group in a
molecule.
9. A polylactic acid resin molded article according to claim 8,
wherein the polar group comprises at least one kind of group
selected from the group consisting of an oxygen-containing
substituent, a nitrogen-containing substituent, and a halogen
group.
10. A polylactic acid resin molded article according to claim 8,
wherein the polar group comprises at least one kind of group
selected from the group consisting of a hydroxyl group, a glycidyl
group, a carboxyl group, an amino group, a nitro group, a cyano
group, and an isocyanate group.
11. A polylactic acid resin molded article according to claim 8,
wherein the at least one kind of low molecular compound selected
from a carboxylic acid amide and a carboxylic acid ester each of
which has a polar group in a molecule comprises an
ethylenebis-12-hydroxystearic acid amide.
12. A polylactic acid resin molded article according to claim 8,
wherein the polylactic acid resin composition contains 100 parts by
mass or less of a fiber with respect to 100 parts by mass of the
polylactic acid resin.
13. A polylactic acid resin molded article according to claim 12,
wherein the fiber comprises at least one kind of fiber selected
from a plant-derived fiber, a synthetic organic fiber, and an
inorganic fiber.
14. A polylactic acid resin molded article according to claim 12,
wherein the fiber has an average fiber length of 80 .mu.m to 3 mm
after being mixed with the polylactic acid resin.
15. A method of manufacturing a polylactic acid resin molded
article, comprising setting a mold temperature to a glass
transition temperature of a polylactic acid resin plus 20.degree.
C. or higher and a melting point thereof minus 20.degree. C. or
lower, at the time of injection molding a polylactic acid resin
composition comprising a polylactic acid resin reacted with a
(meth)acrylate compound and at least one kind of low molecular
compound selected from a carboxylic acid amide and a carboxylic
acid ester each of which has a polar group in a molecule.
16. A method of manufacturing a polylactic acid resin molded
article according to claim 15, wherein the polar group comprises at
least one kind of group selected from the group consisting of an
oxygen-containing substituent, a nitrogen-containing substituent,
and a halogen group.
17. A method of manufacturing a polylactic acid resin molded
article according to claim 15, wherein the polar group comprises at
least one kind of group selected from the group consisting of a
hydroxyl group, a glycidyl group, a carboxyl group, an amino group,
a nitro group, a cyano group, and an isocyanate group.
18. A method of manufacturing a polylactic acid resin molded
article according to claim 15, wherein the at least one kind of low
molecular compound selected from a carboxylic acid amide and a
carboxylic acid ester each of which has a polar group in a molecule
comprises an ethylenebis-12-hydroxystearic acid amide.
19. A method of manufacturing a polylactic acid resin molded
article according to claim 15, wherein the polylactic acid resin
composition contains 100 parts by mass or less of a fiber with
respect to 100 parts by mass of the polylactic acid resin.
20. A method of manufacturing a polylactic acid resin molded
article according to claim 19, wherein the fiber comprises at least
one kind of fiber selected from the group consisting of a
plant-derived fiber, a synthetic organic fiber, and an inorganic
fiber.
21. A method of manufacturing a polylactic acid resin molded
article according to claim 19, wherein the fiber has an average
fiber length of 80 .mu.m to 3 mm after being mixed with the
polylactic acid resin.
Description
TECHNICAL FIELD
[0001] This invention relates to a polylactic acid resin
composition and a molded item or article using the polylactic acid
resin composition.
BACKGROUND ART
[0002] In recent years, resins formed of plant-derived materials
have been drawing attention from the viewpoint of environmental
conservation. Among the resins formed of plant-derived materials,
polylactic acid is one of the resins having the highest heat
resistance and capable of mass production, so polylactic acid can
be obtained at a low cost and is highly useful. The recent
applications thereof varies widely from applications having short
period of service time based on an assumption that the resin will
be discarded, e.g., a container and packing and an agricultural
film, to highly functional applications which can retain initial
properties for a long period of time, e.g., housings of home
electric appliances and OA equipment and automobile parts.
[0003] Polylactic acid is a crystalline resin, and it is important
that the resin be crystallized in order to exhibit the original
material properties thereof, such as heat resistance. However,
polylactic acid has a low crystallization rate, so the
crystallization thereof does not proceed sufficiently when molded
in a short period of time and has tendencies that the heat
resistance, elastic modulus, and the like thereof decrease.
[0004] Accordingly, as a method of improving the moldability of
polylactic acid, a method of increasing the crystallization rate of
polylactic acid has been proposed. For example, in Japanese Patent
No. 3411168 (Patent Document 1), it is described that a molded
article retaining its transparency and crystrallizability can be
obtained by adding a transparent nucleating agent such as aliphatic
amide to aliphatic polyesters, such as polylactic acid.
[0005] Further, Japanese Unexamined Patent Application Publication
No. 2003-226801 (Patent Document 2) describes that the
crystallization rate of polylactic acid is significantly increased
by adding a low molecular compound having an amide group and a
layered clay mineral organized with an organic onium salt to
polylactic acid.
[0006] Further, in order to increase the crystallization rate, a
method of adding a (meth)acrylate compound to polylactic acid is
also disclosed (for example, see Japanese Unexamined Patent
Application Publication No. 2003-128901 (Patent Document 3)).
[0007] When the transparent nucleating agent, such as aliphatic
amide, exemplified in Patent Document 1 is added to polylactic
acid, an increase in crystallization rate of polylactic acid can be
observed compared with the case of an additive-free polylactic
acid. However, the effect of the addition is not sufficient,
therefore, in order to obtain a molded article having a sufficient
crystallinity, a heat treatment after molding is required. Further,
because a crystallinity of polylactic acid is low, the crystal
solidification in a mold at the time of, for example, injection
molding, is tend to be insufficient. As a result, there are some
defects such that the molded article is deformed at the time of
mold releasing.
[0008] Further, when a low molecular compound having amide group
and a layered clay mineral organized with an organic onium salt
disclosed in Patent Document 2 are added to polylactic acid, an
increase in crystallization rate and an improvement in moldability
of polylactic acid can be observed compared with the cases of the
additive-free polylactic acid and polylactic acid being added with
the nucleating agent such as aliphatic amide, but the effects
thereof are insufficient. Further, in the resin composition
described in Patent Document 3, the crystallization rate is
increased, but the effects thereof are not necessarily sufficient
in some cases.
DISCLOSURE OF THE INVENTION
Problems to be solved by the Invention
[0009] An object of the present invention is accomplished in view
of the problems inherent in the above-mentioned conventional
technology, and to provide a polylactic acid resin composite
material having an excellent moldability at a crystallization
temperature of the polylactic acid resin, and a molded article
using the same.
Means to solve the Problems
[0010] The inventors of the present invention have intensively
studied to solve the above problems. As a result, they have
completed a polylactic acid composite material of the present
invention in which the moldability thereof is being remarkably
improved compared with that of the conventional material, at the
time of molding the polylactic acid resin at the temperature at
which the polylactic acid resin is crystallized, by adding a
carboxylic acid amide and a carboxylic acid ester each of which has
a polar group in a molecule to a polylactic acid resin reacted with
a (meth)acrylate compound. In addition, they have also found that
the moldability of the polylactic acid resin is further improved by
adding a fiber thereto.
[0011] That is, according to an aspect of the present invention,
there is provided a polylactic acid resin composition including a
polylactic acid resin reacted with a (meth)acrylate compound and at
least one kind of low molecular compound selected from a carboxylic
acid amide and a carboxylic acid ester each of which has a polar
group in a molecule. Here, in the present invention, each of an
acrylate compound and a methacrylate compound is collectively
referred to as a (meth)acrylate compound.
[0012] Further, in the polylactic acid resin composition of the
present invention, it is preferable that the polar group preferably
includes at least one kind of group selected from the group
consisting of an oxygen-containing substituent, a
nitrogen-containing substituent, and a halogen group.
[0013] Further, in the polylactic acid resin composition of the
present invention, it is preferable that the polar group preferably
includes at least one kind of group selected from the group
consisting of a hydroxyl group, a glycidyl group, a carboxyl group,
an amino group, a nitro group, a cyano group, and an isocyanate
group.
[0014] Further, in the polylactic acid resin composition of the
present invention, it is preferable that the low molecular compound
preferably includes an ethylenebis-12-hydroxystearic acid
amide.
[0015] Further, in the polylactic acid resin composition of the
present invention, it is preferable that the polylactic acid resin
composition preferably contains 100 parts by mass or less of a
fiber with respect to 100 parts by mass of the polylactic acid
resin, and it is more preferable that the fiber include at least
one kind of fiber selected from a plant-derived fiber, a synthetic
organic fiber, and an inorganic fiber, or the fiber have an average
fiber length of 80 .mu.m to 3 mm after being mixed with the
polylactic acid resin.
[0016] Further, according to another aspect of the present
invention, there is provided a polylactic acid resin molded
article, which is obtained by molding a polylactic acid resin
composition, in which the polylactic acid resin composition
includes a polylactic acid resin reacted with a (meth)acrylate
compound and at least one kind of low molecular compound selected
from a carboxylic acid amide and a carboxylic acid ester each of
which has a polar group in a molecule.
[0017] Here, in the polylactic acid resin molded article of the
present invention, it is preferable that the polar group preferably
includes at least one kind of functional group selected from the
group consisting of an oxygen-containing substituent, a
nitrogen-containing substituent, and a halogen group.
[0018] Further, in the polylactic acid resin molded article of the
present invention, it is preferable that the polar group preferably
includes at least one kind of group selected from the group
consisting of a hydroxyl group, a glycidyl group, a carboxyl group,
an amino group, a nitro group, a cyano group, and an isocyanate
group.
[0019] Further, in the polylactic acid resin molded article of the
present invention, it is preferable that the low molecular compound
preferably includes an ethylenebis-12-hydroxystearic acid
amide.
[0020] Further, in the polylactic acid resin molded article of the
present invention, it is preferable that the polylactic acid resin
composition preferably contains 100 parts by mass or less of a
fiber with respect to 100 parts by mass of the polylactic acid
resin, and it is more preferable that the fiber include at least
one kind of fiber selected from a plant-derived fiber, a synthetic
organic fiber, and an inorganic fiber, or the fiber have an average
fiber length of 80 .mu.m to 3 mm after being mixed with the
polylactic acid resin.
[0021] Further, according to another aspect of the present
invention, there is provided a method of manufacturing a polylactic
acid resin molded article, including setting a mold temperature to
a glass transition temperature of a polylactic acid resin plus
20.degree. C. or higher and a melting point thereof minus
20.degree. C. or lower, at the time of injection molding a
polylactic acid resin composition including a polylactic acid resin
reacted with a (meth)acrylate compound and at least one kind of low
molecular compound selected from a carboxylic acid amide and a
carboxylic acid ester each of which has a polar group in a
molecule.
[0022] Here, in the method of manufacturing a polylactic acid resin
molded article according to the present invention, it is preferable
that the polar group preferably includes at least one kind of group
selected from the group consisting of an oxygen-containing
substituent, a nitrogen-containing substituent, and a halogen
group.
[0023] Further, in the method of manufacturing a polylactic acid
resin molded article according to the present invention, it is
preferable that the polar group preferably includes at least one
kind of group selected from the group consisting of a hydroxyl
group, a glycidyl group, a carboxyl group, an amino group, a nitro
group, a cyano group, and an isocyanate group.
[0024] Further, in the method of manufacturing a polylactic acid
resin molded article according to the present invention, it is
preferable that the at least one kind of low molecular compound
selected from a carboxylic acid amide and a carboxylic acid ester
each of which has a polar group in a molecule preferably includes
an ethylenebis-12-hydroxystearic acid amide.
[0025] Further, in the method of manufacturing a polylactic acid
resin molded article according to the present invention, it is
preferable that the polylactic acid resin composition preferably
contains 100 parts by mass or less of a fiber with respect to 100
parts by mass of the polylactic acid resin, and it is more
preferable that the fiber include at least one kind of fiber
selected from a plant-derived fiber, a synthetic organic fiber, and
an inorganic fiber or the fiber have an average fiber length of 80
.mu.m to 3 mm after being mixed with the polylactic acid resin.
EFFECT OF THE INVENTION
[0026] As an effect of this invention, a polylactic acid resin
composition that gives a molded article which is unlikely to be
deformed even when molded in a short period of time and a molded
article of a polylactic acid resin are provided.
BEST MODE FOR EMBODYING THE INVENTION
[0027] Hereinafter, embodiments of the present invention are
described in detail.
[0028] A polylactic acid resin composition of the present invention
has a constitution which includes a polylactic acid resin reacted
with a (meth)acrylate compound and at least one kind of low
molecular compound selected from a carboxylic acid amide and a
carboxylic acid ester each of which has a polar group in a
molecule.
[0029] Further, a polylactic acid resin molded article or part of
the present invention is a molded article which is obtained by
molding the polylactic acid resin composition.
[0030] Further, a method of manufacturing the polylactic acid resin
molded article of the present invention includes setting a mold
temperature to a glass transition temperature of a polylactic acid
resin composition plus 20.degree. C. or higher and a melting point
thereof minus 20.degree. C. or lower, at the time of injection
molding the polylactic acid resin composition.
[0031] Specifically, the polylactic acid resin composition of the
present invention is a composition in which a carboxylic acid amide
and a carboxylic acid ester each of which has a polar group in a
molecule are added to a polylactic acid resin reacted with a
(meth)acrylate compound.
[0032] Further, the polylactic acid resin composition of the
present invention contains a kenaf fiber and other fibers.
[0033] As the polylactic acid resin of the present invention,
poly(L-lactic acid), poly(D-lactic acid), and a mixture thereof or
a copolymer thereof may be used.
[0034] In the present invention, a melt flow rate of the polylactic
acid resin at 190.degree. C. under a load of 21.2 N (e.g., a value
according to JIS standard K-7210 (condition D of Table 1, Appendix
A)) is preferably 0.1 to 50 g/10 minutes, and more preferably 0.2
to 30 g/10 minutes. In the case where the melt flow rate exceeds 50
g/10 minutes, a melt viscosity of the polylactic acid resin is too
low and a mechanical strength and a heat resistance of the molded
article become poor. In the case where the melt flow rate is less
than 0.1 g/10 minutes, a load to the polylactic acid resin at the
time of molding process becomes too high and an operability of the
polylactic acid resin may be decreased.
[0035] The polylactic acid resin is generally manufactured by a
known melt polymerization method, or by combined use of a solid
phase polymerization method therewith. Further, as methods of
adjusting the melt flow rate of the polylactic acid resin within a
predetermined range, in the case where the melt flow rate is too
high, a method of increasing the molecular weight of the polylactic
acid resin by using a small amount of chain length extender such as
a diisocyanate compound, a bisoxazoline compound) an epoxy
compound, and an acid anhydride is mentioned. On the contrary, in
the case where the melt flow rate is too low, a method of mixing a
polyester resin or a low molecular weight compound, each of which
has a high melt flow rate, with the polylactic acid resin can be
mentioned.
[0036] A content ratio of one of an L-lactic acid unit and a
D-lactic acid unit, which are the constituent components of the
polylactic acid resin, is preferably 85 mol % or more, more
preferably 90 mol % or more, still more preferably 95 mol % or
more, and particularly preferably 98 mol % or more. When the
D-lactic acid unit or the L-lactic acid unit is less than 85 mol %,
there is a tendency that an effect to be obtained is not expressed
sufficiently owing to a decrease in stereoregularity.
[0037] An amount of residual monomers such as lactic acid and
lactide contained in the polylactic acid resin is preferably 0.6
parts by mass or less with respect to 100 parts by mass of the
polylactic acid resin. When the amount of residual monomers exceeds
0.6 parts by mass, a hydrolysis resistance of the polylactic acid
resin may be decreased.
[0038] A plurality of the polylactic acid resins, each of which has
different proportions of the L-lactic acid unit and the D-lactic
acid unit with each other, may be blended together at any
appropriate ratio and used.
[0039] A monomer except for lactic acid which is a main component
may be copolymerized with the polylactic acid resin, and preferably
copolymerized in an amount of preferably 30 mass % or less. For
example, as an acid component, there are given: aromatic
dicarboxylic acids, such as terephthalic acid, isophthalic acid,
orthophthalic acid, 2,6-naphthalene dicarboxylic acid,
2,5-naphthalene dicarboxylic acid, 2,7-naphthalene dicarboxylic
acid, 1,5-naphthalene dicarboxylic acid, methyl terephthalate,
4,4'-biphenyl dicarboxylic acid, 2,2'-biphenyl dicarboxylic acid,
4,4'-biphenyl ether dicarboxylic acid, 4,4'-diphenylmethane
dicarboxylic acid, 4,4'-diphenylsulfone dicarboxylic acid, and
4,4'-diphenylisopropylidene dicarboxylic acid; saturated aliphatic
dicarboxylic acids such as adipic acid, sebacic acid, oxalic acid,
malonic acid, succinic acid, azelaic acid, undecanedioic acid,
dodecanedioic acid, icosanedioic acid, and hydrogenated dimer acid;
unsaturated aliphatic dicarboxylic acids, such as fumaric acid,
maleic acid, itaconic acid, mesaconic acid, citoraconic acid, and
dimer acid, and anhydrides thereof; and alicyclic dicarboxylic
acids, such as 1,4-cyclohexane dicarboxylic acid, 1,3-cyctohexane
dicarboxylic acid, 1,2-cyclohexane dicarboxylic acid,
2,5-norbornene dicarboxylic acid, and tetrahydrophthalic acid. In
addition, as a diol component, an aliphatic diol such as ethylene
gycol, propylene glycol, 1,3-butane diol, diethylene glycol,
neopentyl glycol, 1,5-pentane diol, 1,6-hexane diol, 1,8-octane
diol, or 1,10-decane diol; an alicyclic diol such as
1,4-cyclohexane dimethanol, 1,3-cyclohexane dimethanol, or
1,2-cyclohexane dimethanol; a bisphenol, such as bisphenol A or
bisphenol S, or an ethylene oxide adduct thereof; or an aromatic
diol such as hydroquinone or resorcinol may be copolymerized.
[0040] In addition, a hydroxycarboxylic acid such as
p-hydroxybenzoic acid, p-(2-hydroxyethoxy)benzoic acid,
6-hydroxycaproic acid, 3-hydroxybutanoic acid, or 3-hydroxyvaleric
acid, or a lactone compound such as .delta.-valerolactone,
.gamma.-butyrolactone, or .epsilon.-caprolactone may be
copolymerized. In addition, in order to impart flame retardancy, an
organic phosphorous compound may be copolymerized.
[0041] In the polylactic acid resin component, another polyester
resin, such as polyethylene terephthalate, polycarbonate,
polyarylate, polycyclohexylene dimethylene terephthalate,
polyethylene naphthalate, polybutylene naphthalate, polyethylene
isophthalate/terephthalate, polybutylene
isophthalate/terephthalate, polyethylene
terephthalate/cyclohexylene dimethylene terephthalate,
polycyclohexylene dimethylene isophthalate/terephthalate,
poly(p-hydroxybenzoic acid/ethylene terephthalate), or
polytetramethylene terephthalate may be mixed. Those components are
mixed in an amount of preferably 30 mass % or less with respect to
100 mass % of the polylactic acid resin.
[0042] The (meth)acrylate compound to be used in the present
invention is reacted with the polylactic acid resin, and imparts a
branched structure, a crosslinking structure, a chain length
extension, and the like to the resin. As a result, a melt tension
of the resin increases, and the moldability thereof is further
improved. When at least one of the carboxylic acid amide and the
carboxylic acid ester each of which has a polar group in a
molecule, is added to the polylactic acid resin reacted with the
(meth)acrylate compound, in addition to the improvement in the
moldability owing to the increased melt tension, a different
mechanism of crystallization promotion proceeds simultaneously,
compared with the case where one of the (meth)acrylate compound and
the carboxylic acid amide or the carboxylic acid ester is used
alone. Consequently, a molding cycle is shortened, and it is
considered that the fact leads to the improvement in moldability
such that poses no problems in extracting the molded article even
in the same molding cycle and to the increase in heat
resistance.
[0043] As the (meth)acrylate compound used in the present
invention, preferably, a compound having two or more (meth)acrylic
groups, or a compound having one or more (meth)acrylic group(s) and
one or more glycidyl group(s) or vinyl group(s) in the molecule is
given because such components have high reactivity with the
polylactic acid resin, whereby a monomer hardly remains and the
resin is unlikely colored. Specific examples thereof include
glycidyl methacrylate, glycidyl acrylate, glycerol dimethacrylate,
trimethylolpropane trimethacrylate, trimethylolpropane triacrylate,
allyloxypolyethylene glycol monoacrylate, allyloxypolyethylene
glycol monomethacrylate, polyethylene glycol dimethacrylate,
polyethylene glycol diacrylate, polypropylene glycol
dimethacrylate, polypropylene glycol diacrylate, polytetramethylene
glycol dimethacrylate (alkylene glycol moieties thereof may be
copolymers of alkylene having various lengths), butanediol
methacrylate, and butanediol acrylate. Of those, polyethylene
glycol dimethacrylate, polypropylene glycol dimethacrylate,
ethylene glycol dimethacrylate, and diethylene glycol
dimethacrylate are preferred for safety and reactivity.
[0044] An amount of the (meth)acrylate compound to be used in the
present invention is preferably 0.01 to 20 parts by mass, more
preferably 0.01 to 10 parts by mass, and still more preferably 0.01
to 3 parts by mass with respect to 100 parts by mass of the
polylactic acid resin. When the amount is less than 0.01 part by
mass, the increase in crystallization rate, which is an object of
the present invention, is not sufficient, and thus the heat
resistance and the moidability cannot be obtained. When the amount
exceeds 20 parts by mass, the degree of reaction becomes too high,
which may lead to a trouble in operability.
[0045] The polylactic acid resin reacted with the (meth)acrylate
compound of the present invention may be mixed with a polylactic
acid resin which is unreacted with the (meth)acrylate compound, and
the amount of the polylactic acid resin which is unreacted with the
(meth)acrylate compound is preferably 100 parts by mass or less,
and particularly preferably 50 parts by mass or less with respect
to 100 parts by mass of the polylactic acid resin reacted with the
(meth)acrylate compound. When the amount of the polylactic acid
resin which is unreacted is 50 parts by mass or less, the
moldability of the composition part can be retained further
satisfactorily.
[0046] In the present invention, a peroxide as a reaction assistant
is preferably added concurrently with the (meth)acrylate compound.
As the peroxide, an organic peroxide which has a satisfactory
dispersibility in the resin is preferable. Specific examples
thereof include benzoyl peroxide,
bis(butylperoxy)trimethylcyclohexane,
bis(butylperoxy)methylcyclododecane, butylbis(butylperoxy)valerate,
dicumyl peroxide, butylperoxybenzoate, dibutyl peroxide,
bis(butylperoxy)diisopropylbenzene, dimethyldi(butylperoxy)hexane,
dimethyldi(butylperoxy)hexyne, and butyl peroxycumene. A
compounding amount of the peroxide is preferably 0.02 to 20 parts
by mass, and more preferably 0.1 to 10 parts by mass with respect
to 100 parts by mass of the polylactic acid resin. When the
compounding amount is less than 0.1 part by mass, the effect of
increasing the reactivity is low, and when the compounding amount
exceeds 20 parts by mass, it is not preferable in terms of
cost.
[0047] In order to block a terminal group of the polylactic acid
resin component to increase a humidity-heat resistance, an impact
resistance, and the like, one or more kinds of compounds selected
from carbodiimide compounds may be combined with the polylactic
acid resin composition of the present invention. A compounding
range of the carbodiimide compound is 0.5 to 20 parts by mass, more
preferably 1 to 10 parts by mass, and particularly preferably 1 to
3 parts by mass with respect to 100 parts by mass of the polylactic
acid resin. When the compounding amount is less than 0.5 parts by
mass, any effects on mechanical physical properties such as the
humidity-heat resistance and the impact resistance of the resin
composition of the present invention cannot be observed. On the
other hand, when the compounding amount exceeds 20 parts by mass,
no further effects can be expected.
[0048] The carbodiimide compound is not particularly limited as
long as the compound has one or more carbodiimide group(s) in the
molecule. Examples thereof include
N,N'-di-2,6-diisopropylphenylcarbodiimide,
N,N'-di-o-tolylcarbodiimide, N,N'-diphenylcarbodiimide,
N,N'-dioctyldecylcarbodiimide,
N,N'-di-2,6-dimethylphenylcarbodiimide,
N-tolyl-N'-cyclohexylcarbodiimide,
N,N'-di-2,6-di-tert.-butylphenylcarbodiimide,
N-tolyl-N'-phenylcarbodiimide, N,N'-di-p-nitrophenylcarbodiimide,
N,N'-di-p-aminophenylcarbodiimide,
N,N'-di-p-hydroxyphenylcarbodiimide,
N,N'-di-cyclohexylcarbodiimide, N,N'-di-p-tolylcarbodiimide,
p-phenylene-bis-di-o-tolylcarbodiimide,
p-phenylene-bis-dicyclohexylcarbodiimide,
hexamethylene-bis-dicyclohexylcarbodiimide,
4,4'-dicyclohexylmethanecarbodiimide,
ethylene-bis-diphenylcarbodiimide, N,N'-benzylcarbodiimide,
N-octadecyl-N'-phenylcarbodiimide, N-benzyl-N'-phenylcarbodiimide,
N-octadecyl-N'-tolylcarbodiimide,
N-cyclohexyl-N'-tolylcarbodiimide, N-phenyl-N'-tolylcarbodiimide,
N-benzyl-N'-tolylcarbodiimide, N,N'-di-o-ethylphenylcarbodiimide,
N,N'-di-p-ethylphenylcarbodiimide,
N,N'-di-o-isopropylphenylcarbodiimide,
N,N'-di-p-isopropylphenylcarbodiimide,
N,N'-di-o-isobutylphenylcarbodiimide,
N,N'-di-p-isobutylphenylcarbodiimide,
N,N'-di-2,6-diethylphenylcarbodiimide,
N,N'-di-2-ethyl-6-isopropylphenylcarbodiimide,
N,N'-di-2-isobutyl-6-isopropylphenylcarbodiimide,
N,N'-di-2,4,6-trimethylphenylcarbodiimide,
N,N'-di-2,4,6-triisopropylphenylcarbodiimide,
N,N'-di-2,4,6-triisobutylphenylcarbodiimide,
diisopropylcarbodiimide, dimethylcarbodiimide,
diisobutylcarbodiimide, dioctylcarbodiimide,
t-butylisopropylcarbodiimide, di-.beta.-naphthylcarbodiimide,
di-t-butylcarbodiimide, and aromatic polycarbodiimides. Further,
polymers thereof can be exemplified. Those carbodiimide compounds
may be used alone or two or more kinds thereof may be used in
combination. In the present invention, aromatic carbodiimide,
particularly N,N'-di-2,6-diisopropylphenylcarbodiimide, and a
polymer of the compounds thereof (degree of polymerization thereof
is desirably about 2 to 20) are desirably used. In addition, a
carbodiimide compound having a cyclohexane ring, particularly
4,4'-dicyclohexylmethanecarbodiimide, and a polymer of the
compounds thereof (degree of polymerization thereof is desirably
about 2 to 20) are particularly preferably used. The carbodiimide
compound can be produced by conventionally known methods, for
example, by a carbodiimide reaction which accompanies
decarboxylation reaction using a diisocyanate compound as a
material. At that time, a carbodiimide compound having an
isocyanate group at a terminal end can be obtained unless a
terminal blocking treatment with monoisocyanate or the like is
performed. A concentration of an isocyanate group is not
particularly limited. A specific example of the compound includes
LA-1 manufactured by Nisshinbo Industries, Inc. (aliphatic
carbodiimide compound including 1 to 3% isocyanate group), which is
commercially available.
[0049] Another petroleum-derived resin may be mixed to the
polylactic acid resin composition of the present invention.
Examples of the petroleum-derived resins include: thermoplastic
resins such as polypropylene, ABS, and nylon; and thermosetting
resins such as a phenol resin, a silicone resin, and a furan
resin.
[0050] The carboxylic acid amide and the carboxylic acid ester each
of which has a polar group in a molecule and works as an organic
crystal nucleating agent according to the present invention are
compounds each having molecular weights of 1,000 or less, and more
preferably 100 to 900. When the molecular weight of each of the
compounds exceeds 1,000, the compatibility with the polylactic acid
resin decreases, and thus the dispersibility of the compounds may
be decreased or the compounds may bleed out from the molded
article. As the organic crystal nucleating agent, one kind of
compound may be used alone or two or more kinds thereof may be used
in mixture.
[0051] As a main skeleton of the carboxylic acid amide, an
aliphatic monocarboxylic acid amide, an aliphatic biscarboxylic
acid amide, or an aromatic carboxylic acid amide can be mentioned,
and as the carboxylic acid ester, an aliphatic monocarboxylate, an
aliphatic biscarboxylate, or an aromatic carboxylate can be
mentioned. The number of the amide group or the ester group
contained in each of the compounds may be one or two or more. Of
those, the compounds containing the amide group are preferable,
because they have higher melting point than the case of the
compounds containing the ester group, and can rapidly generate the
crystal nuclei which causes a crystallization of the polylactic
acid resin to occur at the time of molding the polylactic acid
resin composition of the present invention. In addition, a bisamide
is particularly preferable in the point of enabling an increase in
the crystallization rate.
[0052] Specific examples of compound of aliphatic monocarboxylic
acid amides, aliphatic biscarboxylic acid amides, and aromatic
carboxylic acid amides, include lauric acid amide, palmitic acid
amide, oleic acid amide, stearic acid amide, erucic acid amide,
N-oleylpalmitic acid amide, N-oleyloleic acid amide, N-oleyistearic
acid amide, N-stearyloleic acid amide, N-stearyistearic acid amide,
N-stearylerucic acid amide, methylenebisstearic acid amide,
ethylenebislauric acid amide, ethylenebiscapric acid amide,
ethylenebisoleic acid amide, ethylenebisstearic acid amide,
ethylenebiserucic acid amide, ethylenebisisostearic acid amide,
butylenebisstearic acid amide, and p-xylylenebisstearic acid
amide.
[0053] Specific examples of aliphatic monocarboxylate, aliphatic
biscarboxylate, and aromatic carboxylate include laurate,
palmitate, oleate, stearate, erucate, N-oleyl palmitate, N-oleyl
oleate, N-oleyl stearate, N-stearyl oleate, N-stearyl stearate,
N-stearyl erucate, methylenebisstearate, ethylenebislaurate,
ethylenebiscaprate, ethylenebisoleate, ethylenebisstearate,
ethylenebiserucate, ethylenebisisostearate, butylenebisstearate,
and p-xylylenebisstearate.
[0054] As a polar group contained in the carboxylic acid amide and
the carboxylic acid ester of the present invention, any group may
be employed as long as it is selected from an oxygen-containing
substituent, a nitrogen-containing substituent, and a halogen
group. The low molecular compound of the present invention contains
preferably at least two of those polar groups, and an interval
between any two polar groups is preferably 34.+-.4 .ANG. (that is,
3.4.+-.0.4 nm). The interval between two polar groups indicates a
direct distance between carbon atoms each to which the polar group
is bound in the state where the whole molecule is most stretched
while each atom constituting the whole molecule is satisfying a
known bond angle at each bonding. The number of polar groups
contained in the compounds may be three or more. Further, as for
kinds of the polar groups, more specifically, the oxygen containing
substituent includes a hydroxyl group, a glycidyl group, and a
carboxyl group, and the nitrogen-containing substituent includes an
amino group, a nitro group, a cyano group, and an isocyanate group.
Further, different kinds of polar groups may be contained in one
molecule. Note that, in the case where the kinds of the polar
groups contained in a molecule structure is two or more and in the
case where the number of the polar groups is three or more, from an
influence of chemical interaction between the polar groups, the
compound may function preferably also when an interval between two
polar groups selected from the above is in a range of 34.+-.10
.ANG. (that is, 3.4.+-.1.0 nm) in the state where the whole
molecule is most stretched while each atom constituting the whole
molecule is satisfying a known bond angle at each bonding.
[0055] It should be noted that "substitution" according to the
present invention means that a hydrogen atom bound to a carbon atom
in the molecule which does not have a polar group is
substituted.
[0056] As the carboxylic acid amide and the carboxylic acid ester
having the preferable conditions, in which a part of molecule is
substituted with a polar group, for example, there are given
ethylenebis-12-hydroxystearic acid amide,
hexamethylenebis-10-hydroxystearic acid amide,
hexamethylenebis-9,10-dihydroxystearic acid amide,
p-xylylenebis-9,10-dihydroxystearic acid amide,
p-xylylenebis-11,12-dihydroxystearic acid amide,
ethylenebis-12-aminostearic acid amide,
hexamethylenebis-10-aminostearic acid amide,
hexamethylenebis-9,10-diaminostearic acid amide,
p-xylylenebis-9,10-diaminostearic acid amide,
p-xylylenebis-11,12-diaminostearic acid amide,
ethylenebis-12-cyanostearic acid amide,
hexamethylenebis-10-cyanostearic acid amide,
hexamethylenebis-9,10-dicyanostearic acid amide,
p-xylylenebis-9,10-dicyanostearic acid amide,
p-xylylenebis-11,12-dicyanostearic acid amide,
ethylenebis-12-glycidylstearic acid amide,
hexamethylenebis-10-glycidylstearic acid amide,
hexamethylenebis-9,10-diglycidyl stearic acid amide,
p-xylylenebis-9,10-diglycidylstearic acid amide,
p-xylylenebis-11,12-diglycidylstearic acid amide,
ethylenebis-12-hydroxystearate,
hexamethylenebis-10-hydroxystearate,
hexamethylenebis-9,10-dihydroxystearate,
p-xylylenebis-9,10-dihydroxystearate,
p-xylylenebis-11,12-dihydroxystearate,
ethylenebis-12-aminostearate, hexamethylenebis-10-aminostearate,
hexamethylenebis-9,10-diaminostearate,
p-xylylenebis-9,10-diaminostearate,
p-xylyienebis-11,12-diaminostearate, ethylenebis-12-cyanostearate,
hexamethylenebis-10-cyanostearate,
hexamethylenebis-9,10-dicyanostearate,
p-xylylenebis-9,10-dicyanostearate,
p-xylylenebis-11,12-dicyanostearate,
ethylenebis-12-glycidylstearate,
hexamethylenebis-10-glycidylstearate,
hexamethylenebis-9,10-diglycidylstearate,
p-xylylenebis-9,10-diglycidylstearate,
p-xylylenebis-11,12-diglycidyistearate. Of those, a carboxylic acid
amide substituted with a hydroxy group such as
ethylenebis-12-hydroxystearic acid amide,
hexamethylenebis-10-hydroxystearic acid amide,
hexamethylenebis-9,10-dihydroxystearic acid amide,
p-xylylenebis-11,12-dihydroxystearic acid amide, and
p-xylylenebis-9,10-dihydroxystearic acid amide are preferred from
the viewpoint of improvement of a crystallization rate of the
polylactic acid resin. Further, a carboxylic acid bisamide each
having 2 or more and 8 or less methylene groups or 1 or more and 4
or less phenyl group(s) between two amides bonding, and having 3 or
more and 6 or less hydroxy substituents such as
hexamethylenebis-9,10-dihydroxystearic acid amide,
p-xylylenebis-11,12-dihydroxystearic acid amide, and
p-xylylenebis-9,10-dihydroxystearic acid amide are particularly
preferred.
[0057] Further, the melting points of the carboxylic acid amide and
the carboxylic acid ester each of which has a polar group at a
specific site in a molecule are preferably 20 to 300.degree. C.
When the melting point of each of the compounds is lower than
20.degree. C., the compounds may bleed out from the molded article
and an exterior appearance of the molded article tends to be
deteriorated. On the other hand, when the melting point thereof
exceeds 300.degree. C., it becomes difficult to melt the compounds
under a general molding processing conditions, and thus a molding
processability thereof tends to be decreased.
[0058] In the polylactic acid resin composition of the present
invention, a content of the organic crystal nucleating agent which
has a polar group at a specific site in a molecule is preferably
0.1 to 5 parts by mass with respect to 100 parts by mass of the
polylactic acid resin. When the content of the organic crystal
nucleating agent which has a polar group is less than 0.1 part by
mass, a degree of increase in crystallization rate tends to become
insufficient. On the other hand, when the content thereof exceeds 5
parts by mass, a thermoplastic function of the composition comes to
be expressed excessively strongly, which may lead to the tendencies
that the rigidity of the composition decreases, the composition
bleeds out from the molded article, and an exterior appearance of
the molded article is deteriorated being remarkable. More
preferably, the content is 0.5 to 3 parts by mass. When the content
of the organic crystal nucleating agent which has a polar group is
in the above range, the moldability and the state of exterior
appearance after molding is further satisfactory.
[0059] In the present invention, when at least one of the
carboxylic acid amide and the carboxylic acid ester each of which
is the low molecular compound having a polar group in a molecule,
and the (meth)acrylate compound are both added to the polylactic
acid resin, the moldability of the polylactic acid resin is
extremely improved compared with the case where one of the
carboxylic acid amide or the carboxylic acid ester and the
(meth)acrylate compound is used alone. It is considered that the
mechanism which promotes the crystallization to one of the both
compounds differs from that to the other compounds. It is also
considered that the total crystallization rate is increased as a
result of an unexpected multiplier effect of the both, and thus
leading to a shortened molding cycle and to the improvement in
moldability such that poses no problems in extracting the molded
article even in the same molding cycle. In addition, as a result,
the heat resistance is also increased.
[0060] The polylactic acid resin composition of the present
invention can increase its mechanical properties and heat
resistance by including a reactive compound containing at least 1
unit or more of a functional group selected from the group
consisting of an epoxy, an isocyanate, an oxazoline, a
carbodiimide, an acid anhydride, and an alkoxysilane. 0.01 to 5
parts by mass of the reactive compound is preferably contained with
respect to 100 parts by mass of the polylactic acid resin.
[0061] Of the above reactive compounds, as a compound having an
epoxy group, there are exemplified various glycidyl ethers and
various glycidyl esters, such as a glycidyl methacrylate-methyl
methacrylate copolymer, a glycidyl methacrylate-styrene copolymer,
polyethyleneglycol diglycidyl ether, trimethylolpropane
polyglycidyl ether, coconut fatty acid glycidyl ester, an
epoxidized soybean oil, and an epoxidized linseed oil. In addition,
examples of a compound having an isocyanate group include
hexamethylene diisocyanate, tolylene diisocyanate, and
diphenylmethane diisocyanate.
[0062] In addition, specific examples of the oxazoline compound
include 2-methoxy-2-oxazoline, 2-ethoxy-2-oxazoline,
2-propoxy-2-oxazoline, 2,2'-m-phenylenebis(2-oxazoline),
2,2'-tetramethylenebis(2-oxazoline),
2,2'-hexamethylenebis(2-oxazoline),
2,2'-octamethylenebis(2-oxazoline),
2,2'-decamethylenebis(2-oxazoline),
2,2'-ethylenebis(4-methyl-2-oxazoline),
2,2'-tetramethylenebis(4,4'-dimethyl-2-oxazoline), and
2,2'-diphenylenebis(2-oxazoline). Further, polyoxazoline compound
containing the above compound as a monomer unit, such as a
styrene-2-isopropenyl-2-oxazoline copolymer is exemplified. Of
those oxazoline compounds, one kind or two or more kinds of
compounds can be arbitrarily selected.
2,2'-m-phenylenebis(2-oxazoline) and
2,2'-p-phenylenebis(2-oxazoline) are preferred from the viewpoint
of heat resistance, reactivity, and compatibility with a
biodegradable polyester resin.
[0063] In addition, specific examples of the carbodiimide compound
include N,N'-di-2,6-diisopropylphenylcarbodiimide,
N,N'-di-o-tolylcarbodiimide,
N,N'-di-2-isobutyl-6-isopropylphenylcarbodiimide,
N,N'-di-2,4,6-trimethylphenylcarbodiimide,
N,N'-di-2,4,6-triisopropylphenylcarbodiimide,
N,N'-di-2,4,6-triisobutylphenylcarbodiimide, diisopylcarbodiimide,
dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide,
t-butylisopropylcarbodiimide, di-.beta.-naphthylcarbodiimide,
di-t-butylcarbodiimide, aromatic polycarbodiimides, and polymers
thereof. Those may be used alone or two or more kinds thereof may
be used in combination. In the present invention, aromatic
carbodiimides, in particular,
N,N'-di-2,6-diisopropylphenylcarbodiimide and polymers thereof
(having preferably polymerization degree of about 2 to 20) are
desirably used. In addition, an carbodiimide compound having a
cyclohexane ring, in particular,
4,4'-dicyclohexylmethanecarbodiimide and polymers thereof (having
preferably polymerization degree of about 2 to 20) is particularly
preferably used.
[0064] Examples of a compound containing an acid anhydride include
trimellitic anhydride, pyromellitic anhydride, an ethylene-maleic
anhydride copolymer, a methylvinyl ether-maleic anhydride copolymer
and a styrene-maleic anhydride copolymer.
[0065] As a compound containing an alkoxysilane, various
alkyltrialkoxysilanes are used. As an alkoxy group, a methoxy group
and an ethoxy group are suitably used, and as an alkyl group, an
alkyl group substituted with a glycidyl group and isocyanate group
are suitably used. Specific examples of the compound include
glycidoxypropyltrimethoxysilane, glycidoxypropyltriethoxysilane,
isocyanatepropyltriethoxysilane,
methacryloxypropylmethyltrimethoxysilane,
acryloxypropylmethyltrimethoxysilane and olygomers obtained by
subjecting those compounds to dehydrating condensation.
[0066] As the method for the polylactic acid resin to include the
reactive compound, there are a method of mixing the reactive
compound with the resin beforehand and then reacting them, and a
method of mixing the reactive compound simultaneously with the
resin in the same process as the compound to be described below and
reacting them, and any of those methods may be employed. Further,
it is preferable that, in the case where the alkoxysilane is added
at the time of melt-kneading, alcohol generated by the reaction be
removed from a vent port under reduced pressure.
[0067] A content of those reactive compounds in the polylactic acid
resin is preferably 0.1 to 5 parts by mass, more preferably 0.2 to
3 parts by mass, and still more preferably 0.3 to 2 parts by mass
with respect to 100 parts by mass of the polylactic acid resin.
[0068] Further, the polylactic acid resin composition of the
present invention can be imparted with increased heat resistance by
further including a fiber. In the case where the fiber is used, a
content thereof is preferably 150 to 5 parts by mass with respect
to 100 parts by mass of the polylactic acid resin of the present
invention, because the impact resistance and the moldability of the
composition are particularly excellent, and is particularly
preferably 100 to 5 parts by mass.
[0069] As the fiber according to the present invention, plant
fibers, such as a kenaf, synthetic organic fibers such as an aramid
fiber and a whole aromatic polyester fiber, and inorganic fibers,
such as a glass fiber and a metal fiber can be used. One kind
thereof may be used alone, two or more kinds thereof may be used in
mixture, or different kinds of fibers may be used in mixture.
[0070] The plant fiber used for the present invention is a fiber
derived from a plant, and specific examples thereof include fibers
obtained from wood, kenaf, bamboo, and hemps. Those fibers
preferably have an average fiber length of 20 mm or less. Further,
pulp and the like which can be obtained by subjecting those plant
fibers to delignification or depectination are particularly
preferable, because degradation thereof, such as decomposition and
discoloration due to heat is small. The kenaf and the bamboo each
have high photosynthesis rate and the growth thereof is fast, so
they can absorb a large amount of carbon dioxide, therefore they
are excellent as one of the means to simultaneously solve the Earth
problems of global warming caused by carbon dioxide and
deforestation. Thus, the kenaf and the bamboo are preferable among
the plant fibers.
[0071] As the synthetic organic fiber according to the present
invention, polyamide fibers such as an aramid fiber and nylon
fiber, polyester fibers, such as a polyarylate fiber and a
polyethylene terephthalate fiber, an ultrahigh strength
polyethylene fiber, a polypropylene fiber and the like are
mentioned.
[0072] The aramid fiber and the polyarylate fiber are aromatic
compounds, and are particulary desirable, because they have high
heat resistance and high strength compared with other fibers, are
pale in color and thus do not degrade design when added to the
resin, and have low specific gravity.
[0073] As the inorganic fiber according to the present invention, a
carbon fiber, a metal fiber, a glass fiber, metal silicate, an
inorganic oxide fiber, an inorganic nitride fiber, and the like are
mentioned.
[0074] A shape of each of the above fibers, in its cross-section,
is not circular, but is polygonal, amorphous, or convexo-concave.
The shape which has a high aspect ratio and a small fiber diameter
is desirable from the viewpoint that a junction area of the fiber
with the resin becomes larger.
[0075] Further, each of the fibers may be subjected to surface
treatment as needed in order to increase affinity with the resin to
be a base material or to increase entanglement between the fibers.
As surface treatment methods, a treatment by coupling agents such
as silane-based and titanate-based, an ozone treatment or a plasma
treatment, a treatment by an alkylphosphate type surfactant, and
the like are effective. However, the treatment method is not
particularly limited to those, and generally used treatment methods
for surface improvement of the filler can be used.
[0076] In each of the fibers above, an average fiber length before
being mixed with the polylactic acid resin is preferably 100 .mu.m
to 20 mm, and it is particularly effective when the length is in a
range of 100 .mu.m to 10 mm. Further, an average fiber length after
being kneaded is preferably 80 .mu.m to 3 mm.
[0077] The combined use of each of those fibers further suppresses
a decrease in the melt tension of the resin, which brings about an
increase in crystallization rate and an additional improvement in
moldability, and in addition, the heat resistance under high-load
condition is significantly increased owing to a reinforcement
effect of the fiber.
[0078] Other than the above, the polylactic acid resin composition
of the present invention may be added with a pigment, a heat
stabilizer, an antioxidant, a weathering agent, a flame retardant,
a plasticizer, a lubricant, a mold releasing agent, an antistat, a
filler, a crystal nucleating agent, an antibacterial agent, and a
fungicide, as needed. Examples of the heat stabilizer and the
antioxidant include hindered phonols, phosphorus compounds,
hindered amine, sulfur compounds, copper compounds, and halides of
alikali metals. As the flame retardant, a halogen flame retardant,
a phosphorus flame retardant, and an inorganic flame retardant may
be used, but when considering the environment, a non-halogen flame
retardant is preferably used. Examples of the non-halogen flame
retardant include a phosphorus flame retardant, hydrated metal
compounds (aluminum hydroxide, magnesium hydroxide),
nitrogen-containing compounds (melamine-based, guanidine-based),
and inorganic compounds (borate, molybdenum compound). As inorganic
fillers, talc, calcium carbonate, zinc carbonate, silica, alumina,
magnesium oxide, calcium silicate, sodium aluminate, calcium
aluminate, sodium aluminosilicate, magnesium silicate, glass
balloons, carbon black, zinc oxide, antimony trioxide, zeolites,
hydrotalcite, boron nitride, potassium titanate, graphite, and the
like are mentioned. As organic fillers, naturally-occurring
polymers such as starch, cellulose fine particles, wood powders,
bean curd refuse, rice husk, and bran, and modified products
thereof are mentioned. As inorganic crystal nucleating agents,
talc, kaoline, and the like are mentioned, and as organic crystal
nucleating agents, sorbitol compounds, metal salts of benzoic acid
and a compound thereof, phosphate metal salts, rosin compounds, and
the like are mentioned. Examples of the antibacterial agent that
can be used include silver ions, copper ions, and zeolite including
those. Note that a method of compounding those with the polylactic
acid resin composition of the present invention is not particularly
limited.
[0079] The resin composition of the present invention may increase
the heat resistance thereof by promoting crystallization. As a
method therefor, a method of promoting crystallization by cooling
the resin in the mold at the time of injection molding can be
exemplified. In this case, it is preferable that a mold temperature
be retained at a glass transition temperature of the polylactic
acid resin (Tg) plus 20.degree. C. or higher and a melting point
thereof (Tm) minus 20.degree. C. or lower for a predetermined
period of time, and then cooled to Tg or lower. Further, as a
method of promoting crystallization after the molding, it is
preferable that, after directly cooling the resin at the mold
temperature of Tg or lower, the resin be subjected again to the
heat treatment at Tg or higher and Tm minus 20.degree. C. or lower.
As a result, the heat resistance of the molded article is
increased, deflection temperature under load (DTUL) under a
low-load condition (0.45 MPa) is Tg plus 30.degree. C. or higher,
and in the system to which the fiber was added, the DTUL under a
high-load condition (1.8 MPa) is Tg plus 20.degree. C. or
higher.
[0080] As methods of mixing various compounding components of the
polylactic acid resin composition according to present invention is
not particularly limited, and mixing by known mixers such as a
tumbler, a ribbon blender, and an uniaxial or biaxial kneader, and
melt-mixing by an extruder, a roller, and the like are mentioned.
At that time, the combined use of a static mixer or a dynamic mixer
may is effective. It is preferable to use a biaxial extruder in
order to enhance the kneading state.
[0081] The molded article of the present invention is formed by
molding the polylactic acid resin composite material of the present
invention.
[0082] The polylactic acid resin composition of the present
invention may be processed into molded articles of, for example,
electrical and electronic equipment applications such as a casing
of electric appliances, architectural material applications,
automobile parts applications, household product applications,
health-care applications, agriculture applications, and the like,
by using methods such as an injection molding method, a blow
molding method, a film molding method, and a foam molding
method.
[0083] The molded article of the present invention is not
particularly limited in its shape, thickness, and the like, and may
be any of an injection molded product, an extrusion molded product,
a compression molded product, a blow molded product, a sheet, a
film, a yarn, a fabric, and the like. More specifically, housings
of electrical and electronic appliances, films for product
packagings, various containers, automobile parts, and the like are
mentioned. Further, in the case where the molded article of the
present invention is used as a sheet, the molded article may be
laminated with paper or another polymer sheet, so as to be used as
a multi-layered laminate.
[0084] The method of molding the polylactic acid resin composition
of the present invention is not particularly limited, and a known
injection molding method, injection/compression molding method,
compression molding method, or the like, which is a general molding
method required for manufacturing electrical and electronic
equipment, can be used. As for a temperature at the time of
melt-mixing or molding, there may be set a range which is equal to
or higher than the melting temperature of the resin to be a base
material, and in which the plant fiber or the polylactic acid resin
is not thermally deteriorated. On the other hand, the mold
temperature is preferably Tm of the polylactic acid resin
composition minus 20.degree. C. or lower. In the case of promoting
crystallization in the mold in order to increase the heat
resistance of the polylactic acid resin composition, it is
preferable that the mold temperature be retained at Tg plus
20.degree. C. or higher and Tm minus 20.degree. C. or lower for a
predetermined period of time, and then cooled to Tg or lower. On
the contrary, in the case of promoting crystallization afterwards,
it is preferable that, after directly cooling the resin composition
to Tg or lower, the resin composition be subjected again to the
heat treatment at Tg or higher and Tm minus 20.degree. C. or
lower.
EXAMPLE
[0085] An evaluation method of the moldability according to
Examples and Comparative Examples of the present invention is
shown.
[0086] Hereinafter, the present invention is described more
specifically by way of Examples. Measuring methods used for the
evaluation of the resin compositions of Examples and Comparative
Examples are as follows.
[0087] (1) Melt flow rate (MFR)
[0088] The melt flow rate was measured according to JIS standard
K-7210 (condition D of Table 1, Appendix A) at 190.degree. C. under
a load of 21.2 N.
[0089] (2) Moldability
[0090] The resin compositions obtained in Examples and Comparative
Examples were molded by using injection molding machine (IS-80G,
manufactured by TOSHIBA MACHINE CO., LTD.) (cylinder temperature:
preset at 185.degree. C., actual measurement temperature of mold:
85.degree. C. and 105.degree. C.), to thereby obtain test pieces.
As for the moldability, retention time (cooling time) at inside the
mold required for taking out the test pieces which have no warp or
shrinkage was measured, and the measurement was used as an index of
the moldability.
[0091] (3) Flexural Strength, Flexural Elastic Modulus
[0092] The flexural strength and the flexural elastic modulus were
measured in accordance with ISO 178.
[0093] (4) Charpy Impact Strength
[0094] The Charpy impact strength was measured in accordance with
ISO 179.
[0095] (5) Heat Resistance (.degree. C.)
[0096] In accordance with ISO 75, deflection temperatures under
load were measured for a load of 0.45 MPa and a load of 1.8
MPa.
[0097] (6) Fiber Length in Resin after Kneading
[0098] In the system to which the fiber was added, 1 g of the
molded article of the polylactic acid resin composition was
dissolved in 50 ml of chloroform, followed by performing filtration
by using 1,480 mesh stainless steel net and measuring length of the
fibers which were in a field of vision when observed by using an
optical microscope, thereby calculating a number average
length.
[0099] (7) Humidity-Heat Resistance
[0100] After the flexural strength test piece was subjected to a
treatment for 200 hours at 60.degree. C. under humidity of 90% RH,
flexural strength was measured, and strength retention rate was
calculated, and evaluated. The strength retention rate preferably
exceeds 90%.
[0101] Note that materials and auxiliary materials used in Examples
and Comparative Examples are as shown in Table 1.
TABLE-US-00001 TABLE 1 Resin Resin A Polylactic acid
(weight-average molecular weight: 200,000, L-lactic acid: 99%,
D-lactic acid: 1%, melting point: 168.degree. C., MFR: 3 g/10
minutes) Resin B Polylactic acid (weight-average molecular weight:
130,000, L-lactic acid: 99%, D-lactic acid: 1%, melting point:
168.degree. C., MFR: 8 g/10 minutes) Resin C Copolymer of
polylactic acid and aliphatic polyester (Plamate PD150,
manufactured by Dainippon Ink and Chemicals Incorporated) Organic
Ethylenebis-12-hydroxystearic acid amide (EBHSA, nucleating
manufactured by ITOH OIL CHEMICALS CO., LTD.) agent
Ethylenebisstearic acid amide (EBSA, manufactured by ITOH OIL
CHEMICALS CO., LTD.) Hexamethylenebis-9,10-dihydroxystearic acid
amide (HMBSHA, manufactured by ITOH OIL CHEMICALS CO., LTD.)
(Meth)acrylate PEGDM: Polyethyleneglycol dimethacrylate
(manufactured by compound NOF CORPORATION) Additive I Di-t-butyl
peroxide (DBPO, manufactured by NOF CORPORATION) Terminal LA-1:
Polycyclohexylcarbodiimide (LA-1, manufactured by blocking agent
Nisshinbo Industries, Inc.) Fiber Kenaf (average fiber length: 3
mm)
Example 1
Preparation of Polylactic Acid Resin Composition
[0102] 3 parts by mass of ethylenebis-12-hydroxystearic acid amide
and 1 part by mass of a (meth)acrylate compound are melt-kneaded in
100 parts by mass of Resin A by using a biaxial extruder (TEM-37BS,
manufactured by TOSHIBA MACHINE CO., LTD.) under conditions of
barrel temperature: 190.degree. C., rotational frequency of screw:
200 rpm, and discharge: 15 kg/h, whereby pellets of polylactic acid
resin composition were obtained. The pellets were subjected to
molding by the above-mentioned injection molding machine and the
moldability was valued.
Examples 2 to 10
[0103] The polylactic acid resin compositions were prepared
similarly as in Example 1 except that the additives were changed as
shown in Tables 2 and 3 below, and the moldability was
evaluated.
Comparative Example 1
[0104] Resin A was subjected to molding without adding any
compounds by using the same injection molding machine as Example 1,
but the test piece in each condition greatly deformed, and thus no
test piece could be obtained.
Comparative Examples 2 to 9
[0105] The polylactic acid resin compositions were prepared
similarly as in Example 1 except that the additives were changed as
shown in Tables 4 and 5, and the moldabilities thereof were
evaluated.
[0106] The results of evaluation of various physical properties are
collectively shown in Tables 2, 3, 4, and 5 below.
[0107] The resin compositions obtained in Examples 1 to 10 were
excellent in moldability, flexural properties, impact resistance,
and heat resistance. Only the resin composition obtained in Example
10 had an excellent result in humidity-heat resistance.
[0108] Comparative Examples 2, 3, and 4 were not compounded with
the (meth)acrylate compound, and thus were inferior in
moldability.
[0109] Comparative Examples 5, 6, 7, and 9 were not compounded with
EBHSA and/or HMBHSA, and thus were inferior in moldability.
[0110] Comparative Example 8 was not compounded with EBHSA and/or
HMBHSA, and the (meth)acrylate compound, and thus was inferior in
moldability.
TABLE-US-00002 TABLE 2 Example 1 Example 2 Example 3 Example 4
Example 5 Composition Resin A (part(s) by mass) 100 -- -- -- -- B
(part(s) by mass) -- 100 100 100 100 C (part(s) by mass) -- -- --
-- -- Organic nucleating agent EBHSA (part(s) by mass) 3 3 3 3 3
HMBHSA (part(s) by mass) -- -- -- -- -- (Meth)acrylate compound
PEGDM (part(s) by mass) 0.1 0.1 0.2 0.1 0.1 Additive I DBPO
(part(s) by mass) -- 0.2 0.4 0.2 0.2 Fiber Kenaf (part(s) by mass)
-- -- -- 10 20 Terminal blocking agent LA-1 (part(s) by mass) -- --
-- -- -- Average length of fiber in resin after kneading (mm) -- --
-- 1.5 1.5 Physical Moldability Cooling time (second(s), mold: 75
65 60 60 55 properties 85.degree. C.) Cooling time (second(s),
mold: 50 50 45 45 40 105.degree. C.) Flexural Flexural strength
(MPa) 98 101 106 132 143 properties Flexural elastic modulus (GPa)
4.1 4.1 4.3 5.6 6.8 Impact resistance Charpy impact strength
(kJ/m.sup.2) 2.1 2.1 2.0 2.3 2.7 Heat resistance DTUL (.degree. C.,
load: 0.45 MPa) 121 122 121 128 148 DTUL (.degree. C., load: 1.8
MPa) 66 65 65 105 116 Humidity-heat resistance Strength retention
rate (%) 50 56 54 46 42
TABLE-US-00003 TABLE 3 Example 6 Example 7 Example 8 Example 9
Example 10 Composition Resin A (part(s) by mass) -- -- -- -- -- B
(part(s) by mass) 100 80 80 80 100 C (part(s) by mass) -- 20 20 20
-- Organic nucleating agent EBHSA (part(s) by mass) -- 3 -- 3 3
HMBHSA (part(s) by mass) 3 -- 3 -- -- (Meth)acrylate compound PEGDM
(part(s) by mass) 0.1 0.1 0.1 0.1 0.1 Additive I DBPO (part(s) by
mass) 0.2 0.2 0.2 0.2 0.2 Fiber Kenaf (part(s) by mass) 20 -- -- 20
20 Terminal blocking agent LA-1 (part(s) by mass) -- -- -- -- 2
Average length of fiber in resin after kneading (mm) 1.5 -- -- 1.5
1.5 Physical Moldability Cooling time (second(s), 55 70 70 60 55
properties mold: 85.degree. C.) Cooling time (second(s), 40 55 55
45 40 mold: 105.degree. C.) Flexural properties Flexural strength
(MPa) 141 76 75 112 145 Flexural elastic modulus (GPa) 6.8 3.1 3.0
4.6 6.5 Impact resistance Charpy impact strength (kJ/m.sup.2) 2.6
3.1 3.1 3.4 2.8 Heat resistance DTUL (.degree. C., load: 0.45 MPa)
146 114 113 135 147 DTUL (.degree. C., load: 1.8 MPa) 115 64 63 106
115 Humidity-heat resistance Strength retention rate (%) 44 52 53
41 93
TABLE-US-00004 TABLE 4 Comparative Comparative Comparative
Comparative Comparative Example 1 Example 2 Example 3 Example 4
Example 5 Composition Resin A (part(s) by mass) 100 100 -- -- -- B
(part(s) by mass) -- -- 100 80 100 C (part(s) by mass) -- -- -- 20
-- Organic nucleating agent EBHSA (part(s) by mass) -- 3 3 -- --
HMBHSA (part(s) by mass) -- -- -- 3 -- EBSA (part(s) by mass) -- --
-- -- -- (Meth)acrylate compound PEGDM (part(s) by mass) -- -- --
-- 0.1 Additive I DBPO (part(s) by mass) -- -- -- -- -- Fiber Kenaf
(part(s) by mass) -- -- -- -- -- Average length of fiber in resin
after kneading (mm) -- -- -- -- -- Physical Moldability Cooling
time (second(s), not moldable 150 150 150 140 properties mold:
85.degree. C.) Cooling time (second(s), not moldable 90 90 90 85
mold: 105.degree. C.) Flexural properties Flexural strength (MPa)
-- 96 96 74 100 Flexural elastic modulus (GPa) -- 4.0 4.1 3.0 4.2
Impact resistance Charpy impact strength (kJ/m.sup.2) -- 1.8 1.9
3.1 2.2 Heat DTUL (.degree. C., load: 0.45 MPa) -- 117 116 112 119
resistance DTUL (.degree. C., load: 1.8 MPa) -- 62 62 62 65
Humidity-heat resistance Strength retention rate (%) -- 51 52 52
52
TABLE-US-00005 TABLE 5 Comparative Comparative Comparative
Comparative Example 6 Example 7 Example 8 Example 9 Composition
Resin A (part(s) by mass) -- -- -- -- B (part(s) by mass) 100 100
100 100 C (part(s) by mass) -- -- -- -- Organic nucleating agent
EBHSA (part(s) by mass) -- -- -- -- HMBHSA (part(s) by mass) -- --
-- -- EBSA (part(s) by mass) -- -- 3 3 (Meth)acrylate compound
PEGDM (part(s) by mass) 0.1 0.1 -- 0.1 Additive I DBPO (part(s) by
mass) 0.2 0.2 -- 0.2 Fiber Kenaf (part(s) by mass) -- 20 -- --
Average length of fiber in resin after kneading (mm) -- 1.5 -- --
Physical Moldability Cooling time (second(s), mold: 140 120 155 140
properties 85.degree. C.) Cooling time (second(s), mold: 85 80 95
85 105.degree. C.) Flexural properties Flexural strength (MPa) 103
144 105 104 Flexural elastic modulus (GPa) 4.3 6.8 4.7 4.5 Impact
resistance Charpy impact strength (kJ/m.sup.2) 2.1 2.5 2.0 2.1 Heat
resistance DTUL (.degree. C., load: 0.45 MPa) 120 150 121 122 DTUL
(.degree. C., load: 1.8 MPa) 63 118 64 64 Humidity-heat resistance
Strength retention rate (%) 50 44 50 48
INDUSTRIAL APPLICABILITY
[0111] As described above, the polylactic acid resin composition of
the present invention is applicable to the molded articles of
electrical and electronic equipment applications, architectural
material applications, automobile parts applications, household
product applications, health-care applications, agriculture
applications, toys/amusement applications, and the like, by using
methods such as an injection molding method, a film molding method,
a blow molding method, and a foam molding method.
* * * * *